Cysteine trapping

Cysteine Traps phosgene and converts to less harmful metabolites. Yes Insufficient evidence Hospital emergency dept. 

Dong, M., Xu, X., BaU, A. M., Makhotd, J. A., Lam, P. C. H., Pinon, D. I., etal. (2012). Mapping spatial approximations between the amino terminus of secretin and each of the extraceUular loops of its receptor using cysteine trapping. The FASEB Journal, 26(12), 5092—5105. Retrieved from, http //www.hubmed.org/display.cgi uids=22964305. 

The degradation of carbon tetrachloride to COj by a Pseudomonas sp. (Criddle et al. 1990), although a substantial part of the label was retained in nonvolatile water-soluble residues (Lewis and Crawford 1995). The nature of this was revealed by isolation of adducts with cysteine and N,N -dimethylethylenediamine in which intermediates formally equivalent to COCI2 and CSCI2 were trapped, presumably formed by reaction of the substrate with water and a thiol, respectively. Further consideration of these reactions is given in Chapter 7, Part 3. 

The degradation of CCl4 by Pseudomonas sp. strain KC involved formation of intermediate COCI2 that was trapped as a HEPES complex, and by reaction with cysteine (Lewis and Crawford 1995). Further details of the pathway that is mediated by the metabolite pyridine-dithiocarboxylic acid have been elucidated (Lewis et al. 2001). 

FIGURE 5.22 (A) Reaction of an Fmoc-amino acid with 2-chlorotrityl chloride resin.56 The ester bond formed is cleavable by the mild acid, which does not affect tert-butyl-based protectors. (B) Generation of a protected peptide containing cystine by detachment of a chain, deprotection of cysteine residues, and oxidation of the sulfhydryls by the reagent containing iodine. The cations produced are trapped by CF3CH2OH. 

Trifluoroacetic acid removes tert-butyl-based protectors by the S vl mechanism, with the cation being trapped by the trifluoroacetate anion however, the tert-butyl trifluoroacetate produced is an alkylating agent, and the acid is not strong enough to protonate the side chains of methionine, tryptophan, and cysteine, so these are acceptors of tert-butyl. A scavenger is required to prevent their alkylation. Anisole... 

Researchers at Sunesis pharmaceuticals have developed a fragment-based drug discovery method termed tethering [25]. The approach, which is illustrated in Scheme 2.6, shares a number of features with DCC. Whereas protein-directed DCLs equilibrate small molecules via disulfide formation, say, in the presence of a protein that acts as a thermodynamic trap, tethering uses a cysteine residue on the protein surface to reversibly capture small-molecule thiol fragments from solution. Tethering is designed... 

Performing this reaction at 40°C in a closed system fitted with traps for COS and CO- absorption and passing nitrogen through it, 2-4% COS and 18 to 22% CO- were evolved after 16 hours. A two molar excess 01 glutathione released up to 40% of CO- and 5% of COS. The same experiments carried out with cysteine... 

An analogous assay using a radiolabeled soft nucleophile would also be required to complement the hard nucleophile radiolabeled cyanide trapping assay. Investigations into radiolabeled glutathione have proved unsuccessful since the material is unstable due to cross-reactions induced by beta radiation. Alternate soft nucleophiles such as cysteine, N-acetyl cysteine and P-mercaptoethanol all have promise as radiolabeled substances for quantitative trapping experiments since they are more stable than GSH and equally nucleophilic, although clearly these would not be substrates for GST. 

Heme oxygenase expression. Mainstream smoke trapped in phosphate-buffered saline solutions, in Swiss albino 3T3 fibroblasts, produced dose-dependent and transiently elevated expression of heme oxygenase. Heme oxygenase protein and its mRNA were detectable between 1 and 24 hours after exposure to 0.03 puffs (approx 1 cm / mL of medium). A nearly 50-fold increase in the amount of heme oxygenase mRNA was determined after 8 hours of exposure, compared to control levels. A decrease of more than 60% in glutathione levels was observed after the exposure. No elevated amounts of heme oxygenase mRNA appeared in smoke treated-cells when cysteine was exogenously added . 

Reported rate constants for the reaction of 02 with GSH have varied from 102 to > 105 M 1 s. A re-examination of this reaction by spin trapping with DMPO established that earlier studies had been confounded by the direct reduction of the DMPO/ OOH adduct to DMPO/ OH by GSH. Taking account of this reaction, the revised rate constant was reported to be 200 M-1 g-i.25i.2S2 other workers have examined, for example, the effects of GSH and N-acetyl-L-cysteine on lipid peroxidation 253 and the role of GS in the toxicity of the diabetogenic agent alloxan.254 Direct EPR has been used to detect binuclear Cu(II) complexes of homocysteine. The interactions of such complexes with blood-vessel linings may account for the link between elevated homocysteine and atherosclerosis.255... 

Various peptide Michael acceptors have been described as a new class of inactivators for cysteine proteases. 5-7 The carbonyl group of the scissile peptide bond in the substrate is replaced by a nucleophile trapping moiety such as a vinylogous structure. An amino acid vinyl sulfone, l-(methylsulfonyl)-4-phenylbut-l-en-3-amine [H2NCH(Bzl)CH=CHS02Me] and a dipeptide derivative, Gly-HNCH(Bzl)CH=CHS02Me have both been prepared as inhibitors of cysteine proteases, leucine aminopeptidase and dipeptidyl peptidase I, respectively.1 5 A series of peptide vinyl sulfones has been synthesized as potent inhibitors for different cysteine proteases. 1A8 ... 

---